Downloadable Contour Maps of Spheres

Violin maker Michael Darnton wrote a very nice article in American Lutherie #78 explaining the use of contour maps of spherical domes in determining the depth of guitar sides at various points along their length. I wrote a follow up survey article which covered the whole topic of the varying depth of guitar sides which appeared in American Lutherie #84. The issue here stems from the fact that modern so-called flat top guitars generally don't have flat tops (or backs) at all. Rather, the plates are forced into spherical dome shapes. The implication of this doming is that the sides of an instrument with this style of plate vary in depth along their lengths. Calculating the depth of a side at any point along its length can be done by a number of methods, but the method Mr. Darnton suggests is very quick and easy. But it requires a topographic map of the dome that the plate will be forced into. The radii of the contour lines of such a map can be calculated (see Calculating the Sagitta of an Arc) and the map drawn by hand. Or, you can download contour maps here in AutoCAD 2000 .dwg or .dxf, or .pdf format and print them out at the copy shop or on your own large format printer. See the articles above for a more detailed description of the technique for using these maps.

Last updated: September 11, 2018

The downloadable maps here are half maps, and are sized on 24" x 48" pages. You'll need a large format printer (or access to one) to print these out full size.

Download zipped contour maps in AutoCAD 2000 .dwg and .dxf formats

This above zip file contains maps for all common dome radii (12'30') in both AutoCAD 2000 .dwg and .dxf format. The map for each radius is on a separate layer. Below are PDF files for the maps. Again, these are on 24" x 48" pages.

Download (or view) 12' radius contour map in PDF format

Download (or view) 15' radius contour map in PDF format

Download (or view) 20' radius contour map in PDF format

Download (or view) 25' radius contour map in PDF format

Download (or view) 28' radius contour map in PDF format

Download (or view) 30' radius contour map in PDF format

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